Coil springs for AHC (3 Viewers)

[trdcorolla]

I do not see a difference in part numbers between an 06 LX and my random search of an 03 LX.
RH 48231-6A730
LH 48231-6A740

I was expecting the pressure to drop more than it did. I will perform the flush and see what that changes.
Since the springs vary pressure and I am stock with new OEM springs, then I really should not be looking at this with a magnifying glass. I think it's very close to how it would have been when it first rolled off the floor.
Also, the verbiage in the FSM makes me think there is % error in reading when using the "hand-held tester" compared to the gauge. "The cylinder pressure read by the Lexus hand-held tester is estimated by the pump emitted pressure so the pressure is approximately 1.2MPa higher..." This may be the reason why results vary between vehicles and users. I would be curious to compare results with the LSPV gauge (SST) since it would be live pressure and not estimated. Anyone have one of these tools?

View attachment 2650765

I was comparing the LX AHC springs that luckily weren't available when I needed them to the 06/07 Land Cruiser AHC springs that I purchased instead. It was actually on this thread that someone said the RH Landcruiser AHC springs were used in Australian 100's that came equipped 2 gas tanks, hence the assumption of a a higher spring rate. Below are the part numbers I was referring to.

RH 48231-6A770
LH 48231-6A780

I agree with you saying you shouldn't have to deal with this since you are replacing old with new oem, but unfortunately that's not the case with some people of us. Some here are in spec with the temp sensor unplugged on 15-20 year old springs, it looks like both of us were in the opposite camp. Have you gone through the thread:

Definitive list of AHC maintenance items

My nagging "issue" with AHC is wondering if the suspension doesn't feel quite right. I feel bumps pretty well and I subjectively recall an older 100 series land cruiser standard suspension feeling like being on a cloud vs the small cracks in the road. The question is driving me insane when I'm...

forum.ih8mud.com

I learned a lot reading through that whole thread, if you need cliff notes version of it, you can look at this thread:

The ABCs of AHC - How to Measure, Flush, and Adjust all in one place

I initially put this in the Definitive list of AHC maintenance items thread, but at almost 800 posts long and growing, it's going to get buried and the thread itself is very unwieldy. In an attempt to make as focused a summary as possible, I present "The ABCs of AHC." It's intended as a...

forum.ih8mud.com

 

[riffman12]

another King pressure data point:

finally got around to plugging my LX into Techstream after the King spring install.

Before the Kings my rear pressure was up in the high 7.0 range with my ARB bumper, roof tent, rack, and drawer setup in the back (200 lbs ish)

Now with the Kings:

Front pressure: 6.3 Mpa
Rear pressure: 5.4 Mpa

pretty happy with that. It's actually a little under the factory pressure , but should be well within spec once I load up to go camping etc.

 

[acucole]

I just put on 80 series used springs ($80) with a 30mm spacer and 1/2 loaded up pressures went from 9+ to 5.1. RTT, bumpers, 2x swingouts, 4 passengers.

 

[Hulio]

Again thank you IndroCruise for the information. I'm doing other things now but did want to acknowledge your reply. When I get back to the project and before the swap I will search for measured lengths of the -6A730 and 40 springs.

Because this information wants to be free I will again answer my own post with some data.

For my 2004 US LX470 w/AHC posting photos of new rear springs:
RH 48231-6A730, Yellow painted mark, length approx 17 1/2 inch, and
LH 48231-6A740, Green painted mark, length approx 18 1/8 inch.

Thanks to Desert Toy Shop in Mesa for the photos during the swap I paid them to perform.
Somewhat thanks to the dealer who reimbursed me for the swap after I confronted them again with photo documentation.

 

[acucole]

I just put on 80 series used springs ($80) with a 30mm spacer and 1/2 loaded up pressures went from 9+ to 5.1. RTT, bumpers, 2x swingouts, 4 passengers.

and I can still get into L, N, H - thats mostly loaded though. Without the bumpers, RTT and swingouts I think maybe not.

 

[BigGreenLX]

Thought I'd add a question to refresh this thread. I've noticed everyone replacing rear springs but not the front. I have noticed a harsher reaction and sound to bumps in the road coming from the rear of my 98 LX even after full globe replacement with fluid bleed and replacement but figured the fronts also have 356k on them so should be replaced as well.
I've also replaced front 2 AHC and 1 rear AHC sensors after my drivers side broke. Hoping to do a sensor lift of no more than 2" in the front so figured new springs would help keep less stress off the AHC.
Just wondering why more folks dont replace the fronts as well.

 

[socalmtbiker]

Thought I'd add a question to refresh this thread. I've noticed everyone replacing rear springs but not the front. I have noticed a harsher reaction and sound to bumps in the road coming from the rear of my 98 LX even after full globe replacement with fluid bleed and replacement but figured the fronts also have 356k on them so should be replaced as well.
I've also replaced front 2 AHC and 1 rear AHC sensors after my drivers side broke. Hoping to do a sensor lift of no more than 2" in the front so figured new springs would help keep less stress off the AHC.
Just wondering why more folks dont replace the fronts as well.

For me, my pressures remain in normal limits with an aluminum front bumper. Most of my additional weight added is in the back. Adjustments can be made with the torsion bars. I know of a few threads with people having to change their torsion bars due to added weight in the front; steel bumper, winch, 2nd battery.

 

[ylexot]

I added used torsion bars from a non-AHC LC to my LX after I added the bumper and 90lb of winch cantilevered off the front of the frame. I may have been able to torque the original torsion bars far enough to level the pressures, but the bars were available from another cruiser's lift and figured it would be easier to get the desired pressures. 5+ years later, it's worked pretty well.

 

[BigGreenLX]

Seeing as I don't plan on adding weight to front or back I'm thinking ill add new rear springs and see how that changes things.

 

[ylexot]

One thing I really appreciate about the IFS on the 100 is the spring rate can be tuned, increased or decreased, with a few turns of a wrench.

 

[yj668]

When I went to buy new LX AHC springs in 2017 I was told they weren't available so I bought LC AHC springs instead. The new springs and a 30mm spacer got me 6.8 with the temp sensor plugged in and 6.0 with the temp sensor unplugged. That was with when my LX was stock and had a full tank of gas with the 3rd row seats in. I found out later I lucked out, read here on that the 06/07 AHC springs had a slightly higher spring rate for some reason. Last I checked with a roof rack/sliders/skid plates/3rd row my rear was 7.0 with the temp sensor plugged in, I didn't unplug it to check the pressure since i'll probably be upgrading to Kings next year if I get a alum bumper and move my spare tire back there.

Do you think the 06/07 LC AHC Springs will ride harsh on stock-ish load with/without the spacer?

I'm getting my globes that read 6 gradations from L to H replaced. Will probably swap out the rear coil springs at the same time.

 

[kwon-offroad]

Do you think the 06/07 LC AHC Springs will ride harsh on stock-ish load with/without the spacer?

I'm getting my globes that read 6 gradations from L to H replaced. Will probably swap out the rear coil springs at the same time.

No either way. My pressures were high so I bought new AHC springs to replace the old (145k miles) last year for my 06 LC with AHC. It didn't change much, so I added a 20mm spacer. Slight change in pressures. Then added a 10mm on top of that to sum 30mm. Slight change again, but the ride remained totally stock with the ride settings working well.

I may have these for sale soon, as I went King Springs as I'm starting to add weight (and frankly it's a dedicated camping car so it really only leaves the garage loaded up). Let me know if you're interested. Less than 2k miles on these springs and a set of spacers that you can do either 10mm, 20mm, or stack them to get 30mm (they nest into each other).

 

[yj668]

Thanks for the tips, I'm getting new coil springs from Japan along with the globes.
Any idea what's the thickness of the OEM spacers from Toyota?

Seems like OE spacers are 10mm

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[kwon-offroad]

FYI Springs and Spacers for sale

For Sale - Atlanta: 100 Series AHC Springs with 30mm Spacers 2yrs old

Both bought mid 2020. LC was driven 3700 miles in that time span and is 100% stock from a weight perspective and only loaded during trips. The Nolathane spacers are actually a 10mm and 20mm spacer nestled together to make 30mm. They have been double-sided taped together but can be separated if...

forum.ih8mud.com

 

[MattyO]

One thing I really appreciate about the IFS on the 100 is the spring rate can be tuned, increased or decreased, with a few turns of a wr

 

[MattyO]

I am at 7.7 with King Springs. What are people doing when Kings are not enough? I don't think spacers will make a big enough change in pressure since the rear is so far out of spec. Thoughts or ideas on 80 series vs 100 series springs? Other options?

 

[uHu]

I am at 7.7 with King Springs. What are people doing when Kings are not enough? I don't think spacers will make a big enough change in pressure since the rear is so far out of spec. Thoughts or ideas on 80 series vs 100 series springs? Other options?

The answers will depend on what height your are aiming for, how much extra weight your are carrying, and how much that extra weight will vary.

 

[2001LC]

I am at 7.7 with King Springs. What are people doing when Kings are not enough? I don't think spacers will make a big enough change in pressure since the rear is so far out of spec. Thoughts or ideas on 80 series vs 100 series springs? Other options?

I agree with @uHu !

I'll point out why and how to achieve your goals:

Spacer do make a difference, especially with Kings AHC coils.

Rear 7.7Mpa with King AHC coils. Indicates you've either heavy built rig, have a sensor lift or a combination of.

When we add weight like iron bumpers, etc.. The pressure goes up.
When we increase height, with sensor lift. The pressure goes up.
High Mpa means carrying more weight on AHC system (globes). Can also indicated globes weak/failing.
Low Mpa means carrying more weight on Coils & T-bars, than on globes.

Kings AHC Coils with vehicle at stock weight (3rd row and full tank of gas) & height (no sensor lift), will yield 5.4 to 5.8 Mpa rear. Add 30mm spacer and max height (full sensor lift), yields about 4.8Mpa.

I'd start by cross leveling front, by adjusting T-bars. Than measuring height of rear and marking location of sensor arm in slide, as reference points. Than adjusting rear sensor down the slide, until ~5.8Mpa is achieved. Once rear pressure achieved, measure rear height again. If you now find rear height to low for your set-up or desire, and would like rear of vehicle say 20mm higher. Add 20mm spacers to the Kings, and pressure will drop. Then raise rear 20mm, by adjusting the height sensor up until ~5.8Mpa archived. Than adjust rake, by adjust front sensors. Than adjust T-bars to get 6.9Mpa in front.

Notes:

1. When adjust rear only, pressure changes in fronts just a tad. Or vise versa.
2. If pressure to high in front, and AHC T-bars fully CW cranked up. You can re index AHC T-bar "some" to get a little more out of them. But with a heavy built rigs, I swap out the AHC T-bars, with the thicker Land Cruiser T-bars.
3. Once rear height and Mpa achieved. Drop/lower front of vehicle height to get a minimum of 3/4" rake or more, by adjusting sensor. Then adjust T-bars to bring pressure to ~6.9Mpa. I like to carry a tad extra weight on the LC T-bars, depending on what rear comes in at and how much extra weight in front. So I may drop pressure in frt to 6.7Mpa.
4. We do not want excessively high Mpa front or rear. As this indicates carrying extra weight on AHC system. If pressure high, globes life is reduced. To high of Mpa, and system fails.
5. If King coils, spacers and LC T-bars used, and not enough extra weight. AHC system, "may" not lower.

 

[MattyO]

I agree with @uHu !

I'll point out why and how to achieve your goals:

Spacer do make a difference, especially with Kings AHC coils.

Rear 7.7Mpa with King AHC coils. Indicates you've either heavy built rig, have a sensor lift or a combination of.

When we add weight like iron bumpers, etc.. The pressure goes up.
When we increase height, with sensor lift. The pressure goes up.
High Mpa means carrying more weight on AHC system (globes). Can also indicated globes weak/failing.
Low Mpa means carrying more weight on Coils & T-bars, than on globes.

Kings AHC Coils with vehicle at stock weight (3rd row and full tank of gas) & height (no sensor lift), will yield 5.4 to 5.8 Mpa rear. Add 30mm spacer and max height (full sensor lift), yields about 4.8Mpa.

I'd start by cross leveling front, by adjusting T-bars. Than measuring height of rear and marking location of sensor arm in slide, as reference points. Than adjusting rear sensor down the slide, until ~5.8Mpa is achieved. Once rear pressure achieved, measure rear height again. If you now find rear height to low for your set-up or desire, and would like rear of vehicle say 20mm higher. Add 20mm spacers to the Kings, and pressure will drop. Then raise rear 20mm, by adjusting the height sensor up until ~5.8Mpa archived. Than adjust rake, by adjust front sensors. Than adjust T-bars to get 6.9Mpa in front.

Notes:

1. When adjust rear only, pressure changes in fronts just a tad. Or vise versa.
2. If pressure to high in front, and AHC T-bars fully CW cranked up. You can re index AHC T-bar "some" to get a little more out of them. But with a heavy built rigs, I swap out the AHC T-bars, with the thicker Land Cruiser T-bars.
3. Once rear height and Mpa achieved. Drop/lower front of vehicle height to get a minimum of 3/4" rake or more, by adjusting sensor. Then adjust T-bars to bring pressure to ~6.9Mpa. I like to carry a tad extra weight on the LC T-bars, depending on what rear comes in at and how much extra weight in front. So I may drop pressure in frt to 6.7Mpa.
4. We do not want excessively high Mpa front or rear. As this indicates carrying extra weight on AHC system. If pressure high, globes life is reduced. To high of Mpa, and system fails.
5. If King coils, spacers and LC T-bars used, and not enough extra weight. AHC system, "may" not lower.

Some more info. Globes are just replaced a few months back. Sensor lift is maxed out and rig is heavy. Front and rear bumpers with spare tire swing out, roof rack. Have a hitch swing arm for my bike rack. Often haul lots of bikes or my camping trailer. Front pressures are 6.9 so right at spec but it required lots of t-bar cranks and I indexed them at the same time.

I adjusted sensor lift to lowest position. Rear pressure was 6.8. I need a mild sensor lift so I set it mid way on the slider. Pressure was 7.2 in rear at that height. Also lowered the front sensor height to mid way. I need to turn tbars counterclockwise about 5 turns. Will check pressures again then and see. I don’t think spacers can bridge the gap of my current rear pressures. Suggestions or ideas?

 

[2001LC]

Spacer do make a big difference with Kings. Much more so than with stock AHC coils. If you'd like to max sensor lift. I would then add either 20mm or 30mm spacer, depending on your weight and height you'd like. Note: You can stack up to 2 spacer, according to manufacture.

I'd would consider LC T-bars, if you've added weight like with winch and skids with that bumper. LC T-bars may not let you drop to low, if not enough front end weight at stock height. With just an iron front bumper and stock height (~19 3/8"), LC bars likely not needed.

You'll get benefits from this set up.
1) With your new globes, you should be able to dial in frt Mpa as low as you like 6.9Mpa, or even lower and not max the T-bars. Rear pressure, depending on weight and which spacer. You should be able to get ~6Mpa (before adding gear & people).
2) Reducing the pressure, by shift more weight to coils and T-bars. Will save AHC for when needed.
3) If AHC failure happens on the trail, you'll not drop to the rocks w/LC t-bars. (Carry a 30MM socket in your tool kit).

Note:
We set pressure and height, with full tank of gas and vehicle empty (no people or gear). You can play around a bit loading gear and checking pressure. Some do like to set pressure a bit on low side, unloaded. So that when loaded pressure aren't to high. It get into feel of the ride.